The present invention is directed to a sensing device. More particularly, the present invention pertains to a sensing device used to detect the presence or absence of a fluid even when that fluid is aerated.
Level sensors are known in the art. Various types of mechanical, electro-mechanical and electrical sensors are known, and the type of sensor used for any given application will depend upon the application
Fluid level can be determined using, for example, magnetic sensors, float sensors, optical sensors, ultrasonic sensors and the like. Sensors, such as those disclosed in Knowles, U.S. Publication 2010/0024543, and WO 2008/089209, both commonly assigned with the present application, and incorporated herein by reference, use an elongated probe with a transducer operably connected thereto. The transducer is configured to produce compression waves in the probe and circuitry for detecting acoustic energy that is emitted into the liquid when liquid is in contact with the probe.
While such a probe sensor functions well in certain applications, such as discrete water level detection, it does not function well in fluids that may be aerated.
Another type of sensor is a double probe sensor in which the transducer and receiver functions are provided in separate elements (e.g., probes). However, aerated fluid detection is problematic here as well, due to the acoustic waves being scattered by the trapped air bubbles, which effectively block the propagation and detection of the waves.
Accordingly, there is a need for a level sensor that is capable of detecting fluid level in aerated systems.